The interaction of the azidoacetic acid, N3CH2COOH, with an Ag (111) crystal modified by surface carbon has been observed. XPS measurements of C (1s), O (1s), N (1s) and Ag 3d3/2,5/2as a function of the exposure have been used to follow the predominant species rising with the azide adsorption. Dissociative chemisorption occurs at room temperature leading to the formation of molecular nitrogen followed by NCH2COOH, CHx, NCH2CHO, CO, CO2and CN. The interaction is coverage dependent. The adsorption occurs preferentially around the carbon sites located on the silver surface. The surface decomposition can be related to studies developed for the same molecule in the gas phase. Measurements of work function changes are consistent with the XPS results and this combination is a promising approach to study adsorption.